How to add a ghostly "Glow" effect?
Create a Glow Layer

You separate your render into two, the normal render and a glow render, both layers with a transparent background, in the glow layer set all the objects to have the same material (use an emission shader with the color of the glow you want):




Then, you can use this Node Setup in the Compositor:




You have to take into account that, in this example, the lighting is lame, that's why the effect doesn't look realistic, but using the same lighting that your scene will give you great results